Production of heat-treated coiled medium or high carbon steel wire rods



H. D. L. LLOYD, 2,023,735

Dec. 10, 1935.

PRODUCTION OF HEAT TREATED COILED MEDIUM `ORHIGrH CARBON STEEL WIRE RODS Filed April 6,-'1954 s sneetsneet 1 F s ....armmnldw MMIMUM Dec. 10, 1935.

H. D. 1 LLoYD PRODUCTION OF HEAT TREATED COILED MEDIUM OR HIGH CARBON STEEL WIRE RODS Filed April 6, 1954 3 Sheets-Sheet 2 Tal( Dec. 10, 1935. H. D. l.. LLOYD 29023336 PRODUCTION OF HEAT TREATED COILED MEDIUM 0R HIGH lCARBON STEEL WIRE RODS Filed April 6, 1934 3 Sheets-Sheet 5 Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE PRODUCTION OF HEAT-TREATED COILED MEDIUM OR HIGH CARBON STEEL WIRE RODS Application April 6, 1934, Serial No'. 719,374

In Great Britain April 27, 1933 1 Claim.

This invention relates to the production of heat-treated coiled medium or high carbon steel wire rods.

The present method of effecting the heat treatment of steel Wire rods as referred to above is carried out by passing the rod continuously through a long furnace maintained Well above recalescence point and immediately the heated rod leaves the furnace it is subjected to a carefully' regulated rate of cooling in air or other medium. The above process in practice consists of two stages. The first stage comprises the gradual heating of the rod to above therecalescence point which it is believed allows nthe carbon in the steel to pass into solution. The maintenance ofthe heating for a certain period of travel through the furnace provides a certain time element in which it appears that the required growth of grain size is carried into eiect without difficulty.

The second stage is a cooling process and takes place as the rod leaves the heating furnace. Ap-

parently this cooling process causes the steel to pass rapidly through the critical range down to below the recalescence point and xes the carbon evenly spread in solution throughout the sectional area of the metal. The product of the second stage has what is known as a. sorbitic structure as distinct from the pearlitic structure resulting from too slow a rate of cooling on the one hand and as distinct from the martensitic structure resulting from too rapid a rate of cooling on the other hand. As this sorbitic structure is the required structure a carefulregulationl of the rate of cooling is necessary to avoid, as stated, on the one hand a pearlitic structure and on the other hand a martensiticl structure.

The above process, from a heat standpoint, is essentially wasteful because in the iirst place the heat in the rod, as it leaves the rolls, is necessarily lost and, further, heat must be supplied to the rod in the heat .treatment furnace. Furthermore the reheating in the heat treatment furnace produces decarburization of the 'A surface of the rod. Y

'Ihe object of the present invention is to provide an improved process, particularly'from the heat eiciency point of view, for producing a coiled cold rod of the desired structure and of suitable `uniformity of structure throughout its length. `The main difliculty of attaining this object is due to the fact that although the rod, as it leaves the rolls, is of a suitably high temperature above recalescence, it is travelling at a high '55 rate ofspeed which may be, for instance, from 1500 to 3000 feet per minute. It has, therefore, been the practice, as explained above, to cool the rod and then to reheat it, the rate of travel of the reheated rod being comparatively small, say about 5 to 15 feet per minute, since at this low 5 speed the regulated cooling referred to above can be carried into effect.

According to the invention I provide a method of producing coiled medium or high carbon steel rods of sorbite structure which consists in rolling 1o the rods at a temperature substantially above that of a molten quenching medium maintained at a temperature lying between about 450 C., andabout 500 C., immersing the rods in said medium whilst they remain at substantially the 15 rolling temperature thus causing them to be substantially quenched, coiling the rods in the medium Whilst the latter is maintained substantially at the quenching temperature and subsequentlyremcving the rods from the medium. 20

Referring to the accompanying diagrammatic drawings which illustrate a convenient form of apparatus by means of which the present invention may be carried into effect:-

Figure 1 illustrates a. vertical cross-sectional 25 view.

v Figure 2'is a vertical cross-sectional view taken on the line A--Bof Figure 3.

Figure 3 is a plan view.

Figure 4 is an enlarged view partly in side ele- 30 vation and partly in vertical section of the winding head, frame and drum.

Figure 5 is a plan view of the winding head. Figure 6 is a side elevation partly broken away illustrating the driving head, frame and drum, 35

and l Figure '7 is a sectional plan on the line C-D of Figure 4.

In carrying the invention into eiect in one form, by way o'f example, as illustrated in Figures 40 1 to `4, I provide a coiling bath comprising a metal tank a of heat resisting material in a brickwork or other non-conducting setting b, the tank and ysalts or other quenching medium contained therein being heated conveniently by an 45 oil burner c operating through the side of the setting, theA products of combustion being led along suitable surfaces d of the tank and led away to a iiue duct after having communicated the necessary heat to maintain the slats or other quenching medium at a level temperature.

The coiling mechanism comprises a frame e rotating in fixed bearings f and g, the latter being carried in a conveniently disposed support h. The frame e is rotated by means of bevel gears 9' driven from an electric motor lc.

The upper part of the rotating frame e has a hollow centre into which the heated rod m is led direct from the last pass of the nishing rolls n through a tube o curved vat the end nearest the coiling mechanism so as to lead the rod into the hollow centre of the rotating frame. About midway of the rotating frame a tube p is fixed, the upper end of which is concentric with the hollow centre of the rotating frame and the other end is led outwards on a curve to bring the end of the heated rod outside the rotating frame e.

The lower end of the rotating frame e carries a drum' q suspended therefrom by a ball bearing l1- so that the drum is free and not obliged to rotate with the frame. The lower end of this drum has a square projection-s which fits into a square opening in a bottom plate t on which the rod m falls from the tube p to be coiled owing td the rotation of the frame and tube around the iixed drum and plate.

The square projection s prevents the drum from rotating and assists in the coiling process.

After the last end of the coil has left the rolls n and has been coiled upon the plate t around the drum q the plate t which is hinged about an attachment u to the side of the tank is lowered by means of lever arm v operated by hydraulic cylinder w or similar means.

A balance weight :c attached to the lever v through a exible wire rope y works over a pulley 2 so as to return the table t to the original position when the coil has been dropped.

On the lowering of the table t the coil drops on to slide bars 3 supported on a packing piece 'I of channel section in turn carried on an angle bar 8 bolted to lugs 9 cast on the ywalls of thev moved to allow the table tov be lowered empty ready to receive the next coil.

To secure' rapid circulation of the quenching salts. or other quenching medium, a suitable impeller I is xed-td the lower end of the rotating frame as shown in detail in Figure 4 and openings 5 near the centre of plate t and perforations 6 in the lower part of drum q are made in order to allow the quenching medium to cir- 5 culate through the layers of the coil as the wire rod is coiled into place lap by lap on table t.

The salt bath or other heat treating bath should be molten at the desired temperature range, i. e. between about 450 C. and about 10 500 C., and be workable, that is, reasonably easily stirred or circulatedat that temperature.

Rods may be produced by the method described above which possess so'rbitic grain structure and which are suitable for cold working by subsel5 quent wire drawing to withstand high tensile stress. The coil may if desired be entered into the heat treating medium and laid in it in such a manner as to avoid undue disturbance of the bath.

By the above process I am enabled to utilize the heat existing in the rod as it leaves the last pass o'f the rolls in the process of rod rolling at such temperature above the recalescence point as may be suitable to the carbon content of the rod 25 as a preliminary to eiecting the second\ stage of the process of cooling the rod quickly through the critical range (but without quenching out) to secure the sorbitic structure required; I am also enabled to reduce the decarburization of the rod surface.

I claim:

A method of producing coiled medium or high carbon steel rods of sorbite structure which consists in rolling the rods at a temperature substantially above that of a molten quenching medium maintained at/ a temperature lying between about 450 C. and about 500 C., immersing the rods in said medium whilst they remain at substantially ythe rolling temperature thus causing them to be substantially quenched, coiling the rods in the medium whilst the latter is maintained substantially at the quenching temperature and subsequently removing the rods from the medium. f

HENRY DAVID LLEWELLYN LLOYD. 

